EL lamps are typically formed by depositing a number of layers onto a transparent substrate. The layers typically include the transparent substrate, a transparent front electrode, a phosphor layer, two or more dielectric layers, and a rear electrode. Various other layers are often included. When an alternating electric current is applied to the two electrodes, a field is developed, and the phosphor layer emits light. One example of an EL lamp is a night light.
EL lamps powered directly from the AC line, such as standard 120 vrms/60 Hz house power, are susceptible to voltage surges that could breakdown the dielectric insulator used to separate the front and back electrodes of the EL lamp. Surges, also referred to as anomalies, are short duration high voltage spikes that can randomly occur on the AC line. These surges can come from lightning, the local utility, neighbors, and machines sharing the power source. An anomaly may cause EL lamps to fail catastrophically resulting in a slow sustained combustion. The surges can also cause an arc to jump between the front and back electrode conductors, especially if the gap between the electrodes is made smaller because of a manufacturing defect. Defects introduced during the manufacturing process, i.e., ink bleeds that can either electrically short the front and back electrodes or reduce the designed gap between the two electrodes, can cause an EL lamp to fail similarly. A byproduct of the combustion is carbon. The combustion is fed by the high current available from the power source and will continue until current no longer can flow.
The dielectric breakdown or arc could initiate combustion of the EL materials, resulting in the heating up of the EL lamp enclosure leading to the destruction of the device and possible damage to adjacent objects. The combustion is fed by the high current available from the power source and will continue until there is not sufficient current to sustain the heat required to maintain combustion. Since the product of the combustion is carbon, and carbon is conductive, once initiated, the EL lamp can self-destruct. The catastrophic failure has the potential to do physical damage to a dwelling or other premises in which an EL lamp device is installed.